Method and apparatus for electronic meter testing

ABSTRACT

Methods and apparatus for electronically displaying metered electrical energy are disclosed. A first processor receives voltage and current signals and determines electrical energy. The first processor generates an energy signal representative of the electrical energy determination. A second processor, connected to said first processor, receives the energy signal and generates a display signal representative of electrical energy information. A display is connected to receive the display signal and displays the electrical energy information. In a first embodiment it is preferred for the first processor to determine units of electrical energy from the voltage and current signals and to generate an energy signal representative of the determination of such units and the rate at which the units are determined. In another embodiment the first processor meters multiple types of electrical energy and generates energy signals. A first converter is provided for converting an electrical output signal to light. The second processor, connected to said first converter, generates an output signal in response to the energy signals, wherein the generation of the output signal includes the multiplexing of the energy signals into the output signal. In a still further embodiment, the display provides energy flow direction information.

This is a division, of application Ser. No. 07/839,634 filed on Feb. 21,1992, now U.S. Pat. No. 5,537,029, the disclosure of which is hereinincorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of electric utilitymeters. More particularly, the present invention relates to bothelectronic watthour meters and meters utilized to meter real andreactive energy in both the forward and reverse directions.

BACKGROUND OF THE INVENTION

Techniques and devices for metering the various forms of electricalenergy are well known. Meters, such as utility power meters, can be oftwo types, namely, electro-mechanical based meters whose output isgenerated by a rotating disk and electronic based meters whose outputcomponent is generated electronically. A hybrid meter also exists,wherein an electronic register for providing an electronically generateddisplay of metered electrical energy has been combined, usuallyoptically, to a rotating disk. Pulses generated by the rotating disk,for example by light reflected from a spot painted on the disk, areutilized to generate an electronic output signal.

It will be appreciated that electronic meters have gained considerableacceptance due to their increasing reliability and extended ambienttemperature ranges of operation. Consequently, various forms ofelectronic based meters have been proposed which are virtually free ofany moving parts. In the last ten years several meters have beenproposed which include a microprocessor.

Testing of electronic meters has always been a problem. A special modeof register operation known in the industry as the test mode has beenavailable to ease register testing, however, little has been done toimprove overall meter testing. Electronic meters have the potential ofproviding faster test times, multiple metering functions and calibrationof the meter through software adjustment. However, implementing suchfunctions can be expensive and complicated.

Presently, electric utility companies can test mechanical meters with apiece of test equipment which can reflect light off a metered disk todetect a painted spot as the disk rotates. An alternative form oftesting mechanical meters is disclosed in U.S. Pat. No. 4,600,881—LaRocca et al. which describes the formation of a hole in the disk. Alight sensitive device is placed in a fixed position on one side of thedisk. As the disk rotates, and the hole passes over the light sensitivedevice, a pulse is provided indicating disk movement.

Since electronic meters preferably do not contain rotating disks, suchsimple testing techniques cannot be utilized. Consequently, a needexists for an electronic meter having a relatively simple means oftesting the meter.

SUMMARY OF THE INVENTION

The previously described problem is resolved and other advantages areachieved in a method and apparatus for electronically displaying meteredelectrical energy are disclosed. A first processor receives voltage andcurrent signals and determines electrical energy. The first processorgenerates an energy signal representative of the electrical energydetermination. A second processor, connected to said first processor,receives the energy signal and generates a display signal representativeof electrical energy information. A display is connected to receive thedisplay signal and displays the electrical energy information. In afirst embodiment it is preferred for the first processor to aredetermined. In this embodiment it is also preferred for the secondprocessor to generate, in response to the energy signal, a disk signalrepresentative of a rate of disk rotation equivalent to a traditionalelectromechanical meter and display signals are representative of thetotal number of units, the rate at which units are determined and therate of equivalent disk rotation, wherein the display includes separateindicators for each display signal. In another embodiment the firstprocessor, in concurrently determining units of electrical energy,determines watt units, apparent reactive energy units and the rate atwhich such units are determined, wherein the watt units, the apparentreactive energy units and the rate at which such units are determinedare displayed. In still another embodiment, the first processor metersmultiple types of electrical energy and generates energy signals. Afirst converter is provided for converting an electrical output signalto light. The second processor, connected to the first converter,generates an output signal in response to the energy signals, whereinthe generation of the output signal includes the multiplexing of theenergy signals into the output signal. In a still further embodiment,the display provides energy flow direction information.

It is preferred for the display to be a liquid crystal displaycontaining a plurality of visible annunciators. It is especiallypreferred for the second processor to generate the display signal sothat select annunciators are made visible at select times. In thisfashion it is possible to provide an energy usage indicator equivalentto that of a rotating disk. It is especially desirable for the displaysignal to be generated so that the annunciators provide a forward andreverse energy flow indication at a rate faster than an equivalent diskrotation rate. In an especially preferred embodiment, three annunciatorsare located on the display for providing the above indications ofelectrical energy direction. In that embodiment, the annunciators arearranged in a line. The first annunciator is arrow shaped and indicativeof the reverse direction and the third annunciator is arrow shaped andindicative of the forward direction. It is also preferred for the energysignal to be provided to the second processor at a given data rate. Insuch an embodiment it is especially preferred for the second processorto include a data rate display member for displaying on the display therate at which data is being provided to the second processor. In such anembodiment, the direction and both the rate at which data is provided tothe second processor and a signal mimicking the rate of disk rotationcan be displayed. Indicators for each quantity are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood, and its numerousobjects and advantages will become apparent to those skilled in the artby reference to the following detailed description of the invention whentaken in conjunction with the following drawings, in which:

FIG. 1 is a block diagram of an electronic meter constructed inaccordance with the present invention;

FIGS. 2A-2E combine to provide a flow chart of the primary programutilized by the microcontroller disclosed in FIG. 1;

FIG. 3 is a front elevation of the liquid crystal display shown in FIG.1;

FIG. 4 is a diagrammatic view of select annunciators of the liquidcrystal display shown in FIG. 3;

FIG. 5 is a schematic diagram of the optical port shown in FIG. 1; and

FIG. 6 is a schematic diagram of certain command buttons contained inthe meter.

DETAILED DESCRIPTION

A new and novel meter for metering electrical energy is shown in FIG. 1and generally designated 10. It is noted at the outset that this meteris constructed so that the future implementation of higher levelmetering functions can be supported.

Meter 10 is shown to include three resistive voltage divider networks12A, 12B, 12C; a first processor—an ADC/DSP (analog-to-digitalconverter/digital signal processor) chip 14; a second processor—amicrocontroller 16 which in the preferred embodiment is a MitsubishiModel 50428 microcontroller; three current sensors 18A, 18B, 18C; a 12 Vswitching power supply 20 that is capable of receiving inputs in therange of 96-528 V; a 5 V linear power supply 22; a non-volatile powersupply 24 that switches to a battery 26 when 5 V supply 22 isinoperative; a 2.5 V precision voltage reference 28; a liquid crystaldisplay (LCD) 30; a 32.768 kHz oscillator 32; a 6.2208 Mhz oscillator 34that provides timing signals to chip 14 and whose signal is divided by1.5 to provide a 4.1472 MHz clock signal to microcontroller 16; a 2kbyte EEPROM 35; a serial communications line 36; an option connector38; and an optical communications port 40 that may be used to read themeter. The inter-relationship and specific details of each of thesecomponents is set out more fully below.

It will be appreciated that electrical energy has both voltage andcurrent characteristics. In relation to meter 10 voltage signals areprovided to resistive dividers 12A-12C and current signals are inducedin a current transformer (CT) and shunted. The output of CT/shuntcombinations 18A-18C is used to determine electrical energy.

First processor 14 is connected to receive the voltage and currentsignals provided by dividers 12A-12C and shunts 18A-18C. As will beexplained in greater detail below, processor 14 converts the voltage andcurrent signals to voltage and current digital signals, determineselectrical energy from the voltage and current digital signals andgenerates an energy signal representative of the electrical energydetermination. Processor 14 will always generate watthour delivered (WhrDel) and watthour received (Whr Rec) signals, and depending on the typeof energy being metered, will generate either volt amp reactive hourdelivered (VARhr Del)/volt amp reactive hour received (VARhr Rec)signals or volt amp hour delivered (VAhr Del)/volt amp hour received(VAhr Rec) signals. In the preferred embodiment, each transition onconductors 42-48 (each transition from logic low to logic high and viceversa) is representative of the measurement of a unit of energy. Secondprocessor 16 is connected to first processor 14. As will be explained ingreater detail below, processor 16 receives the energy signal(s) andgenerates an indication signal representative of the energy signal(s).

In relation to the preferred embodiment of meter 10, currents andvoltages are sensed using conventional current transformers (CT's) andresistive voltage dividers, respectively. The appropriate multiplicationis accomplished in a new integrated circuit, i.e. processor 14. Althoughdescribed in greater detail in relation to FIG. 1, processor 14 isessentially a programmable digital signal processor (DSP) with built inanalog to digital (A/D) converters. The converters are capable ofsampling three input channels simultaneously at 2400 Hz each with aresolution of 21 bits and then the integral DSP performs variouscalculations on the results.

Meter 10 can be operated as either a demand meter or as a so-called timeof use (TOU) meter. It will be recognized that TOU meters are becomingincreasingly popular due to the greater differentiation by whichelectrical energy is billed. For example, electrical energy meteredduring peak hours will be billed differently than electrical energybilled during non-peak hours. As will be explained in greater detailbelow, first processor 14 determines units of electrical energy whileprocessor 16, in the TOU mode, qualifies such energy units in relationto the time such units were determined, i.e. the season as well as thetime of day.

All indicators and test features are brought out through the face ofmeter 10, either on LCD 30 or through optical communications port 40.Power supply 20 for the electronics is a switching power supply feedinglow voltage linear supply 22. Such an approach allows a wide operatingvoltage range for meter 10.

In the preferred embodiment of the present invention, the so-calledstandard meter components and register electronics are for the firsttime all located on a single printed circuit board (not shown) definedas an electronics assembly. This electronics assembly houses powersupplies 20, 22, 24 and 28, resistive dividers 12A-12C for all threephases, the shunt resistor portion of 18A-18C, oscillator 34, processor14, processor 16, reset circuitry (not shown), EEPROM 35, oscillator 32,optical port components 40, LCD 30, and an option board interface 38.When this assembly is used for demand metering, the billing data isstored in EEPROM 35. This same assembly is used for TOU meteringapplications by merely utilizing battery 26 and reprogramming theconfiguration data in EEPROM 35.

Consider now the various components of meter 10 in greater detail.Primary current being metered is sensed using conventional currenttransformers. It is preferred for the current transformer portion ofdevices 18A-18C have tight ratio error and phase shift specifications inorder to limit the factors affecting the calibration of the meter to theelectronics assembly itself. Such a limitation tends to enhance the easewith which meter 10 may be programmed. The shunt resistor portion ofdevices 18A-18C are located on the electronics assembly described aboveand are preferably metal film resistors with a maximum temperaturecoefficient of 25 ppm/°C.

The phase voltages are brought directly to the electronic assembly whereresistive dividers 12A-12C scale these inputs to processor 14. In thepreferred embodiment, the electronic components are referenced to thevector sum of each line voltage for three wire delta systems and toearth ground for all other services. Resistive division is used todivide the input voltage so that a very linear voltage with minimalphase shift over a wide dynamic range can be obtained. This incombination with a switching power supply allows the wide voltageoperating range to be implemented.

It will be appreciated that energy units are calculated primarily frommultiplication of voltage and current. The specific formulae utilized inthe preferred embodiment, are described in greater detail in U.S. Pat.No. 5,555,508, to Murday et. al. and incorporated herein by reference.However, for purposes of FIG. 1, such formulae are performed inprocessor 14.

The M37428 microcontroller 16 is a 6502 (a traditional 8 bitmicroprocessor) derivative with an expanded instruction set for bit testand manipulation. This microcontroller includes substantialfunctionality including internal LCD drivers (128 quadraplexedsegments), 8 kbytes of ROM, 384 bytes of RAM, a full duplex hardwareUART, 5 timers, dual clock inputs (32.768 kHz and up to 8 MHz), and alow power operating mode.

During normal operation, processor 16 receives the 4.1472 MHz clock fromprocessor 14 as described above. Such a clock signal translates to a1.0368 MHz cycle time. Upon power fail, processor 16 shifts to the32.768 KHz crystal oscillator 32. This allows low power operation with acycle time of 16.384 kHz. During a power failure, processor 16 keepstrack of time by counting seconds and rippling the time forward. Onceprocessor 16 has rippled the time forward, a WIT instruction is executedwhich places the unit in a mode where only the 32.768 kHz oscillator andthe timers are operational. While in this mode a timer is setup to “wakeup” processor 16 every 32,768 cycles to count a second.

While power supply 20 can be any known power supply for providing therequired direct current power, a preferred form power supply 20 isdescribed, in detail in U.S. Pat. No. 5,457,621, to Munday et al. whichis incorporated herein by reference.

Consider now the main operation of processor 16 in relation to FIGS.2A-2E and FIG. 3. At step 1000 a reset signal is provided tomicrocontroller 16. A reset cycle occurs whenever the voltage levelV_(dd) rises through approximately 2.8 volts. Such a condition occurswhen the meter is powered up.

At step 1002, microcontroller 16 performs an initialize operation,wherein the stack, pointer is initialized, the internal ram isinitialized, the type of liquid crystal display is entered into thedisplay driver portion of microcontroller 16 and timers which requiresinitialization at power, up are initialized. It will be noted that theoperation of step 1002 does not need to be performed for each powerfailure occurrence. Following a power failure, microcontroller 16 atstep 1004 returns to the main program at the point indicated when thepower returns.

Upon initial power up or the return of power after a power failure,microcontroller 16 performs a restore function. At step 1006,microcontroller 16 disables pulses transmitted by processor 14. Thesepulses are disabled by providing the appropriate signal restore bit. Thepresence of this bit indicates that a restore operation is occurring andthat pulses generated during that time should be ignored. Having set thesignal restore bit, microcontroller 16 determines at step 1008 whetherthe power fail signal is present. If the power fail signal is present,microcontroller 16 jumps to the power fail routine at 1010. In the powerfail routine, the output ports of microcontroller 16 are written lowunless the restore bit has not been set. If the restore bit has not beenset, data in the microcontroller 16 is written to memory.

If the power fail signal is not present, microcontroller 16 displayssegments at step 1012. At this time, the segments of the display areilluminated using the phase A potential. It will be recalled that phaseA potential is provided to microcontroller 16 from processor 14. At1014, the UART port and other ports are initialized at 1016, the powerfail interrupts are enabled such that if a falling edge is sensed fromoutput A of processor 14, an interrupt will occur indicating powerfailure. It will be recalled that processor 14 compares the referencevoltage VREF to a divided voltage generated by the power supply 20.Whenever the power supply voltage falls below the reference voltage apower fail condition is occurring.

At step 1018, the downloading of the metering integrated circuit isperformed. It will be appreciated that certain tasks performed bymicrocontroller 16 are time dependent. Such tasks will require a timerinterrupt when the time for performing such tasks has arrived.

At 1022, the self-test subroutines are performed. Although no particularself-tests subroutine is necessary in order to practice the presentinvention, such subroutines can include a check to determine if properdisplay data is present. It is noted that data is stored in relation toclass designation and that a value is assigned to each class such thatthe sum of the class values equals a specified number. If any displaydata is missing, the condition of the class values for data which ispresent will not equal the specified sum and an error message will bedisplayed. Similarly, microcontroller 16 compares the clock signalgenerated by processor 14 with the clock signal generated by watchcrystal 32 in order to determine whether the appropriate relationshipexists.

Having completed the self-test subroutines, the ram is re-initialized at1024. In this re-initialization, certain load constants are cleared frommemory. At 1026, various items are scheduled. For example, the displayupdate is scheduled so that as soon as the restore routine is completed,data is retrieved and the display is updated. Similarly, opticalcommunications are scheduled wherein microcontroller 16 determineswhether any device is present at optical port desired to communicate.Finally, at 1028 a signal is given indicating that the restore routinehas been completed. Such a signal can include disabling the signalrestore bit. Upon such an occurrence, pulses previously disabled willnow be considered valid. Microcontroller 16 now moves into the mainroutine.

At 1030, microcontroller 16 calls the time of day processing routine. Inthis routine, microcontroller 16 looks at the one second bit of itsinternal and determines whether the clock needs to be changed. Forexample, at the beginning and end of Daylight Savings Time, the clock ismoved forward and back one hour, respectively. In addition, the time ofday processing routine sets the minute change flags and date changeflags. As will be appreciated hereinafter, such flags are periodicallychecked and processes occur if such flags are present.

It will be noted that there are two real time interrupts scheduled inmicrocontroller 16 which are not shown in FIG. 2, namely the roll minuteinterrupt and the day interrupt. At the beginning of every minute,certain minute tasks occur. Similarly, at the beginning of every day,certain day tasks occur. Since such tasks are not necessary to thepractice of the presently claimed invention, no further details need beprovided.

At 1032, microcontroller 16 determines whether a self-reprogram routineis scheduled. If the self-reprogram routine is scheduled, such routineis called at 1034. The self-reprogram typically programs in new utilityrates which are stored in advance. Since new rates have beenincorporated, it will be necessary to also restart the display. Afteroperation of the self-reprogram routine, microcontroller 16 returns tothe main program. If it is determined at 1032 that the self-reprogramroutine is not scheduled, microcontroller 16 determines at 1036 whetherany day boundary tasks are scheduled. Such a determination is made bydetermining the time and day and searching to see whether any day tasksare scheduled for that day. If day tasks are scheduled, such tasks arecalled at 1038. If no day tasks are scheduled, microcontroller 16 nextdetermines at 1040 whether any minute boundary tasks have beenscheduled. It will be understood that since time of use switch pointsoccur at minute boundaries, for example, switching from one use periodto another, it will be necessary to change data storage locations atsuch, a point. If minute tasks are scheduled, such tasks are called at1042. If minute boundary tasks have not been scheduled, microcontroller16 determines at 1044 whether any self-test have been scheduled. Theself-tests are typically scheduled to occur on the day boundary. Asindicated previously, such self-tests can include checking theaccumulative display data class value to determine whether the sum isequal to a prescribed value. If self-tests are scheduled, such tests arecalled at 1046. If no self-tests are scheduled, microcontroller 16determines at 1048 whether any season change billing data copy isscheduled. It will be appreciated that as season changes billing datachanges. Consequently, it will be necessary for microcontroller 16 tostore energy metered for one season and begin accumulating energymetered for the following season. If season change billing data copy isscheduled, such routine is called at 1050. If no season change routineis scheduled, microcontroller 16 determines at 1052 whether theself-redemand reset has been scheduled. If the self-redemand reset isscheduled, such routine is called at 1054. This routine requiresmicrocontroller 16 to in effect read itself and store the read value inmemory. The self-redemand is then reset. If self-redemand reset has notbeen scheduled, microcontroller 16 determines at 1056 whether a seasonchange demand reset has been scheduled. If a season change demand resetis scheduled, such a routine is called at 1058. In such a routine,microcontroller 16 reads itself and resets the demand.

At 1060, microcontroller 16 determines whether button sampling has beenscheduled. Button sampling will occur every eight milliseconds.Reference is made to FIG. 6 for a more detailed description of anarrangement of buttons to be positioned on the face of meter 10.Consequently, if an eight millisecond period has passed, microcontroller16 will determine that button sampling is scheduled and the buttonsampling routine will be called at 1062. If button sampling is notscheduled, microcontroller 16 determines at 1064 whether a displayupdate has been scheduled. This routine causes a new quantity to bedisplayed on LCD 30. As determined by the soft switch settings, displayupdates are scheduled generally for every three-six seconds. If thedisplay is updated more frequently, it may not be possible to read thedisplay accurately. If the display update has been scheduled, thedisplay update routine is called at 1066. If a display update has notbeen scheduled, microcontroller 16 determines at 1068 whether anannunciator flash is scheduled. It will be recalled that certainannunciators on the display are made to flash. Such flashing typicallyoccurs every half second. If an annunciator flash is scheduled, such aroutine is called at 1070. It is noted in the preferred embodiment thata directional annunciator will flash at the same rate at which energydetermination pulses are transmitted from processor 14 to processor 16.Another novel feature of the invention is that other annunciators (notindicative of energy direction) will flash at a rate approximately equalto the rate of disk rotation in an electro-mechanical meter used in asimilar application.

If no annunciator flash is scheduled, microcontroller 16 determines at1072 whether optical communication has been scheduled. It will berecalled that every half second microcontroller 16 determines whetherany signal has been generated at optical port. If a signal has beengenerated indicating that optical communications is desired, the opticalcommunication routine will be scheduled. If the optical communicationroutine is scheduled, such routine is called at 1074. This routinecauses microcontroller 16 to sample optical port 40 for communicationsactivity. If no optical routine is scheduled, microcontroller 16determines at 1076 whether processor 14 is signaling an error. Ifprocessor 14 is signaling an error, microcontroller 16 at 1078 disablesthe pulse detection, calls the download routine and after performance ofthat routine, re-enables the pulse detection. If processor 14 is notsignaling any error, microcontroller 16 determines at 1080 whether thedownload program is scheduled. If the download program is scheduled, themain routine returns to 1078 and thereafter back to the main program.

If the download program has not been scheduled or after the pulse detecthas been re-enabled, microcontroller 16 determines at 1082 whether awarmstart is in progress. If a warmstart is in progress, the power failinterrupts are disabled at 1084. The pulse computation routine is calledafter which the power fail interrupts are re-enabled. It will be notedthat in the warmstart data is zeroed out in order to provide a freshstart for the meter. Consequently, the pulse computation routineperforms the necessary calculations for energy previously metered inplaces that computation in the appropriate point in memory. If awarmstart is not in progress, microcontroller 16 at 1084 updates theremote relays. Typically, the remote relays are contained on a boardother than the electronics assembly board.

All data that is considered non-volatile for meter 10, is stored in a 2kbytes EEPROM 35. This includes configuration data (including the datafor memory 76 and memory 80), total kWh, maximum and cumulative demands(Rate A demands in TOU), historic TOU data, cumulative number of demandresets, cumulative number of power outages and the cumulative number ofdata altering communications. The present billing period TOU data isstored in the RAM contained within processor 16. As long as themicrocontroller 16 has adequate power, the RAM contents and real timeare maintained and the microcontroller 16 will not be reset (even in ademand register).

LCD 30 allows viewing of the billing and other metering data andstatuses. Temperature compensation for LCD 30 is provided in theelectronics. Even with this compensation, the meter's operatingtemperature range and the LCD's 5 volt fluid limits LCD 30 to beingtriplexed. Hence, the maximum number of segments supported in thisdesign is 96. The display response time will also slow noticeably attemperatures below −30 degrees Celsius. For a more complete descriptionof the generation of a display signal for display 30, reference is madeto U.S. Pat. No. 5,457,621, Munday et. al. which is incorporated hereinby reference.

The 96 available LCD segments, shown in FIG. 3, are used as follows. Sixdigits (0.375 high) are used for data display and three smaller digits(0.25 high) for numeric identifiers. In addition to the numericidentifiers, there are seventeen alpha annunciators that are used foridentification. These are: PREV, SEAS, RATE, A, B, C, D, CONT, CUM,RESETS, MAX, TOTAL, KV /, \, −\, R, and h. The last five annunciatorscan be combined to produce: KW, KWh, KVA, KVAh, KVAR, or KVARh, asshown. Three potential indicators are provided on the LCD and appear aslight bulbs. These indicators operate individually and are oncontinuously when the corresponding phase's potential is greater than57.6 Vrms, and flash when the potential falls below 38.4 Vrms. “TEST”“ALT”, and “EOI” annunciators are provided to give an indication of whenthe unit is in test mode, alternate scroll mode, or an end of a demandinterval has occurred. Six (6) pulse indicators 200-210 are alsoprovided on LCD 30 for watt-hours and an alternate quantity (VA-hours orVAR-hours).

Pulse indicators 200-210 are configured as two sets of three, one setfor indicating watts and another set for indicating VARhours. Each sethas a left arrow, a solid square, and a right arrow. During any test,one of the arrows will be made to blink at the rate microcontoller 16receives pulses from processor 14 while the square will blink at a lowerrate representative of a disk rotation rate and in a fashion whichmimics disk rotation. It will be noted that signals necessary to flashindicators 200-210 are generated by processor 16 in energy pulseinterrupt routines. The left arrow 200 blinks when energy is receivedfrom the metered site and the right arrow 204 blinks when energy isdelivered to the metered site. The solid square 202 blinks at a Kh rateequivalent to an electro-mechanical meter of the same form, testamperes, and test voltage. Square 202 blinks regardless of the directionof energy flow. The rate at which square 202 blinks can be generated bydividing the rate at which pulses are provided to processor 16.Consequently, testing can occur at traditional rates (indicative of diskrotation) or can occur at faster rates, thereby reducing test time.Indicators 206-210 operate in a similar fashion, except in relation toapparent reactive energy flow.

These pulse indicators can be detected through the meter cover using thereflective assemblies (such as the Skan-A-Matic C42100) of existing testequipment. As indicated above, the second set of three indicatorsindicate apparent reactive energy flow and have the tips of arrows 206and 210 open so that they will not be confused with the watt-hourindicators.

Referring to FIG. 4, it will be seen that annunciators 200-204 arepositioned along a line, wherein annunciator 202 is positioned betweenannunciators 200 and 204. As time progresses, processor 16 generatesdisplay signals so that, when energy is flowing in the forwarddirection, annunciator 204 always flashes. However, annunciators 200 and202 can be made to flash selectively, to create the impression thatenergy is flowing from left to right. When energy is flowing in thereverse direction, the reverse is true. Annunciator 200 flashescontinuously, and annunciators 202 and 204 flash selectively to mimicenergy flowing from right to left.

Meter 10 interfaces to the outside world via liquid crystal display 30,optical port 40, or option connector 38. It is envisioned that mostutility customers will interface to LCD 30 for testing of the meter,some utilities will desire an infrared LED, such as LED 112, to test themeter calibration. Traditionally, electronic meters have provided asingle light emitting diode (LED) in addition to an optical port tooutput a watthour pulse. Such designs add cost, decrease reliability andlimit test capabilities. The present invention overcomes theselimitations by multiplexing the various metering function output signalsand pulse rates over optical port 40 alone. Meter 10 echoes the kh valuewatthour test output on optical port 40 anytime the meter has beenmanually placed in the test mode (the TEST command button in FIG. 5 hasbeen pressed) or alternate scroll mode (the ALT command button in FIG. 5has been pressed). While in these manually initiated modes,communication into processor 16 through optical port 40 is prevented. Itis noted that in the preferred embodiment, the ALT button is capable ofbeing enabled without removal of the meter cover (not shown). To thisend a small movable shaft (not shown) is provided in the meter cover sothat when the shaft is moved the ALT component is enabled. Consequently,removal of the meter cover is not necessary in order to test the meter.

Referring now to FIG. 5, optical port 40 and reset circuitry 108 areshown in greater detail. Optical port 40 provides electronic access tometering information. The transmitter and receiver (transistors 110 and112) are 850 nanometer infrared components and are contained in theelectronics assembly (as opposed to being mounted in the cover).Transistors 110 and led 112 are tied to UART include withinmicrocontroller 16 and the communications rate (9600 baud) is limited bythe response time of the optical components. The optical port can alsobe disabled from the UART (as described below), allowing the UART to beused for other future communications without concern about ambientlight. During test mode, optical port 40 will echo the watthour pulsesreceived by the microcontroller over the transmitting LED 112: toconform to traditional testing practices without the necessity of anadditional LED.

Meter 10 also provides the ability to be placed in the test mode andexit from the test mode via an optical port function, preferably with adata command. When in a test mode initiated via optical port 40, themeter will echo metering pulses as defined by the command transmitted onthe optical port transmitter. This allows the multiplexing of meteringfunctions or pulse rates over a single LED. In the preferred embodiment,such a multiplexing scheme is a time based multiplexing operation. Themeter will listen for further communications commands. Additionalcommands can change the rate or measured quantity of the test outputover optical port 40. The meter will “ACK” any command sent while it isin the test mode and it will. “ACK” the exit test mode command. While inan optically initiated test mode, commands other than those mentionedabove are processed normally. Because there is the possibility of anechoed pulse confusing the programmer-readers receiver, a command tostop the pulse echo may be desired so communications can proceeduninterrupted. If left in test mode, the usual test mode time out ofthree demand intervals applies.

The data command identified above is called “Enter Test Model” and isfollowed by 1 data byte defined below. The command is acknowledged byprocessor 16 the same as other communications commands. The commandplaces meter 10 into the standard test mode. While in this mode,communications inter-command timeouts do not apply. Hence, thecommunications session does not end unless a terminate session commandis transmitted or test mode is terminated by any of the normal ways ofexiting test mode (pressing the test button, power failure, etc.),including the no activity timeout. Display 30 cycles through the normaltest mode display sequence (see the main program at 1044, 1060 and 1064)and button presses perform their normal test mode functions.Transmitting this command multiple times causes the test mode, and itsassociated timeout counter, to restart after each transmission.

The data byte defines what input pulse line(s) to processor 16 should bemultiplexed and echoed over optical port 40. Multiple lines can be setto perform a totalizing function. The definition of each bit in the databyte is as follows:

bit0=alternate test pulses,

bit1=alternate delivered pulses,

bit2=alternate received pulses,

bit3=whr test pulses,

bit4=whr delivered pulses,

bit5=whr received pulses,

bits 6 and 7 are unused.

If no bits are set, the meter stops echoing pulses. This can be used toallow other communications commands to be sent without fear of datacollision with the output pulses. While in this mode, othercommunications commands can be accepted. The test data can be read, themeter can be reprogrammed, the billing data can be reset or a warmstartcan be initiated. Since the Total KWH and Maximum Demand information isstored to EEPROM 35, test data is being processed in memory areas andfunctions such as demand reset and warmstart will operate on the TestMode data and not the actual billing data. Any subsequent “Enter TestMode Command” resets the test mode data just as a manual demand resetwould in the test mode.

This command also provides the utility with a way to enter the test modewithout having to remove the meter cover. This will be beneficial tosome utilities.

While the invention has been described and illustrated with reference tospecific embodiments, those skilled in the- art will recognize thatmodification and variations may be made without departing from theprinciples of the invention as described herein above and set forth inthe following claims.

What is claimed is:
 1. An apparatus for electronically displayingmetered electrical energy, said metered electrical energy beingdetermined from voltage and current signals representative of voltageand current characteristics, said apparatus comprising: a firstprocessor, connected to receive said voltage and current signals, formetering multiple types of electrical energy from said voltage andcurrent signals and for generating energy signals representative of saidmultiple types of electrical energy; a second processor, connected tosaid first processor, for receiving said energy signals and formultiplexing said energy signals into a pulsed output signalrepresentative of a magnitude of said energy signals; and a firstconverter, connected to said second processor, for converting saidpulsed output signal to light.
 2. The apparatus of claim 1, wherein saidfirst converter comprises a light emitting diode.
 3. The apparatus ofclaim 1, wherein said second processor generates said output signal bytime multiplexing said energy signals, whereby energy signals resultingfrom different meter functions can be transmitted from said firstconverter.
 4. The apparatus of claim 1, wherein said second processormultiplexes only certain of said energy signals in response to a controlsignal.
 5. The apparatus of claim 1, further comprising a secondconverter for converting light into an electrical signal.
 6. Theapparatus of claim 5, wherein those portions output by said secondprocessor are determined by a communication signal transmitted to saidsecond processor through said second converter.
 7. The apparatus ofclaim 1, wherein said first processor generates said energy signals sothat said energy signals are further representative of the rate at whicheach of said multiple types of electrical energy are metered.
 8. Theapparatus of claim 7, wherein said second processor generates saidoutput signal by time multiplexing said energy signals, whereby the rateat which each of said multiple types of electrical energy are meteredcan be transmitted from said first converters.
 9. The apparatus of claim8, wherein said second processor generates, in response to said energysignals, disk signals representative of a rate of disk rotation inrelation to said rate at which each of said multiple types of electricalenergy are metered.